Continuous press

ABSTRACT

A continuous press has two rotatively driven endless conveyor belts forming opposed, substantially linear spans defining a pressing zone, press platens applying pressure and temperature through these traveling spans to work carried therebetween, and anti-friction means such as a multiplicity of endless loops of rotatively unpowered roller chains interposed between the platens and the spans. Such a press is improved in that means are provided for regulating the temperature of the edge portions of the conveyor belts which extend beyond the bed of roller chains on each side of the press.

United States Patent 1191 Ahrweiler [45] Dec. 16, 1975 CONTINUOUS PRESS 2,602,960 7 1952 Fischbein 425/371 [751 Inventor Karl-Heinz Ahrwefler, Krefeldy i'lii Z1132; fllifififflijjjj?"""iiijjj iii/5%? 3,408,690 11/1968 Jacob 425/371 x [73] Assignee: Eduard Kusters, Krefeld-Forstwald,

Germany Primary ExaminerRobert L. Spicer, Jr. [22] Filed: Sept. 4, 1973 ltatrorrrgyggpeilt, 0r Fzrm-Kenyon & Kenyon Resilly [21] Appl. No.: 394,105

- [57] ABSTRACT [30] Forelgn Apphcamm Prmmy Data A continuous press has two rotatively driven endless Sept. 4, 1972 Germany 2243465 cOnVyOr belts forming opposed Substantially linear spans defining a pressing zone, press platens applying [52] US. Cl. 425/174.4; 100/151, 100/154; pressure and temperature through these traveling 51 I Cl 2 7 425/371 Spans to work carried therebetween, and anti-friction B29! 5/04 B29C 15/00 means such as a multiplicity of endless loops of rota- 1 d 0 Search 425/8O tively unpowered roller chains interposed between the 3 174A platens and the spans. Such a press is improved in that 17 100/151 154 means are provided for regulating the temperature of the edge portions of the conveyor belts which extend [56] References C'ted beyond the bed of roller chains on each side of the UNITED STATES PATENTS press 2,075,735 3/1937 Loomis 425/72 X 2,559,365 7 1951 Middeton et al. 425/397 x 8 Clams 3 Drawmg Flgures US. Patent Dec. 16, 1975 3,926,542

CONTINUOUS PRESS BACKGROUND OF THE INVENTION This invention relates to continuous presses of the type including endless loops formed by longitudinally and transversely flexible conveyor belts which form opposed, substantially linear spans defining a pressing zone. Means are provided for rotatively driving one or both of the loops to drive the spans in the same direction, and press platens apply pressure and temperature through the traveling spans to the work carried therebetween. A multiplicity of endless loops of roller chains are interposed between each platen and its corresponding belt span and transmit pressure and temperature from the platen to the belt. Such presses are used for the manufacture of wood-chip board, laminated products, minerally-bonded construction boards or plates, for sintering sheets of polytetrafluorethylene, etc. A press of this nature is described in US. Pat. application Ser. No. 308,556 filed Nov. 12, 1972, now US. Pat. No. 3,851,685 issued Dec. 3, 1974.

In presses of this kind the belt spans usually extend transversely beyond the edges of the bed of roller chains so as to avoid clogging of the roller chains by the material to be pressed, for example, wood-chips, some which may fall over the edgesof the belt.

Many of the products manufactured on presses of this kind require elevated temperature for their formation. For example, this is true of resinoid-bonded materials. The necessary heat is supplied to the material being treated by heating the platens, the heat from the platens being transmitted through the roller chains to the belts and thus, to the work. Such a manner of heating naturally works directly only in the limits of the bed of the roller chains, so that the edges of the belt extending beyond the roller chains will have a lower temperature. Because of the resultant differing thermal expansion within the belts, considerable stresses will result in the colder edges of the belts. A further degree of stress in the belts results from strictly mechanical reasons, because the belts are somewhat compressed and therefore stretched longitudinally in a plurality of locations in the area of pressure application through the roller chains; the edge areas of the belts extending beyond the rollers, of course, are not so stretched. Further mechanical stresses on the other hand, tending to lead to a contraction of the middle portion of the belts result from the small bulges forming in the belts in the area of the roller chains between the rollers.

As a result of these differing stresses in the belt spans, longitudinal waves in the nature of bulges are formed therein which are extraordinarily bothersome, for example, when it is desired to loosely distribute the material to be treated evenly on the belt. The resulting tensile stresses further result in substantial material stress which, when superimposed upon the bending stresses to which the endless belt loop is subject when it is reversed in direction at the end of the pressing zone and again at the beginning of the pressing zone can result in tearing at the edges of the belt.

SUMMARY OF THE INVENTION The present invention provides an arrangement for regulating the temperature in the edge portion of the belt spans in a press of this kind, thus reducing the undesirable stresses otherwise present in the belt spans. In accordance with the invention, a temperature regulating arrangement is provided which independently can regulate the temperature of the edge portions of the belt spans which extend beyon the width of the pressure and temperature transmitting elements, i.e., beyond the width of the bed of roller chains. In this manner theseedge portions of the belt spans can be influenced to reduce the undesirable stresses within the belts. It can also take the form of effecting, by tempe rature and the consequent expansion of the edge portions, an equalization of the longitudinal variations in the pressure applying area of the belt mechanically caused by the roller chains. The degree of regulation is dependent upon the stress differences in the particular press operating under particular conditions and can be adjusted manually on the basis of observation or automatically.

For the manufacture of products on presses of the kind for which the invention is applicable generally elevated temperatures are necessary. In these cases the edge portions of the belt spans are at a lower tempera ture than the area of the belt spans through which pressure and temperature are transmitted to the work. In such case, the invention is embodied in a heating arrangement through which the edge portions of the belt spans are heated.

The invention can also be embodied in a converse arrangement in which the edge portions of the belt spans must be cooled.

In the embodiment of the invention a longitudinal channel through which a fluid heat carrier medium flows is positioned at the edge of the belt span and extends the length of the pressure applying zone. In the preferred embodiment, the heat carrier medium is a heating medium, such as hot air or another hot gas or a hot liquid which is pumped through the channel and gives off its heat to the outside, that is, to the edge portion of the belt span through the appropriately formed wall of the channel. The channel can be an air duct positioned at the edge of the belt on the side thereof, away from the material to be treated, the air duct having an opening extending along its length directed toward the adjacent edge of the bed of roller chains. The outer wall of the duct adjacent the edge portion of the belt span is positioned very close to the edge portion of the belt span and is provided with longitudinal ridges which operate in manner of alabyrinth seal.

The hot air passes through the opening against the belt span edge and heats this edge directly. The heat radiating through the wall of the air duct and the longitudinal ridges adjacent the edge of the belt span also heats the edge of the belt. Furthermore in this manner, a certain degree of excess pressure is maintained in the area of the edge of the bed of roller chains, tending to prevent the introduction of dirt into the roller chain bed. The longitudinal ridges of the air duct, functioning as a labyrinth seal help maintain this excess pressure.

In another embodiment rod-shaped electric heating elements can be positioned parallel to the direction of travel of the belts near the edges thereof.

In both the above embodiments the heating of the edge sectors of the belt spans is accomplished primarily by radiation.

It is also possible having to provide an electric heating means operating directly on the edge portion of the belt span, for example, an inductive heating arrangement can be provided. In another embodiment also involving the direct heating of the edges of the belt, contact elements engaging the edge portions of the belt are provided and heating is accomplished in the form of resistance heating between these elements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 show a continuous press having a massof resin-bonded wood-chips pressed together between opposed endless conveyor belts having a heating channel.

FIG. 2 shows another embodiment in which infrared heating elements are provided.

FIG. 3 shows a further embodiment in which an inductive heating arrangement is provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 the work 1 is shown comprising a mass of resinbonded wood-chips pressed together between opposed, substantially linear spans 2 and 3 of two endless conveyor belt loops made of steel of l to I .5 mm thickness.

Pressure and temperature are transmitted from pressure platens through endless loops of a multiplicity of roller chains 4 to corresponding belt spans 2 and 3. Each platen includes a heating plate 5 having channels 6 extending therethrough transversely to the direction of travel of the belts, the channels being connected at their ends by elbows 7. A heating medium pumped into the resulting endless channel brings the heating plate to its proper temperature and heat is thus transmitted through the rollers 4 to each belt span 2 and 3 and is thus applied to the work 1. Each pressure platen further includes a return guide plate 8 having grooves 9 through which the roller chains 4 loop around the platen in a longitudinal direction.

The forces exerted on the material to be pressed between the belt span are taken up by beams 10 which are merely suggested in FIG. 1. Pairs of beams above and below the upper and lower belt spans respectively are connected at their ends beyond the edges of the belt spans by spindles or hydraulic power elements, so that they can press together the work through the return guide plates 8, the heating plates 5 and the roller chains 4. The belt spans 2 and 3 extend transversely beyond the edges of the heating plates 5 and beyond the edge of the beds of roller chains 4. The edge area in which the belts extend beyond the edge of the heating plate and the roller chains being indicated in FIG. 1 by reference numeral 11. In the area of the belt spans 2 and 3 in contact with the roller chains 4, heat is transmitted directly from the heating plates through the roller chains to the spans. Theis is not the case in the edge area 11. Consequently, in that area the temperature of the belts 2 and 3 is lower than in the pressure area of the belts.

In order to counter this temperature differential, the embodiment of FIG. 1 includes heating channels 12 which extend in the direction of travel of the belts along the edge of the spans 2 and 3 in the pressure zone. Hot air is blown through these heating channels 12 in order to heat the edges of the belt spans 2 and 3. Heating the edges of the belt span tends to equalize both the strsses caused by the higher temperature in the central portion of the belt spans, as well as the mechanical stresses caused by the stretching of the span by'the pressure of the rollers. The transmission of heat occurs on the one hand directly through the opening 13, through which the hot air is blown directly against the edges of the belt spans, and, on the other hand, indirectly through radiation from the heated walls of the heating channel 12. To augment this radiation, the portion 14 of the wall of the heating channel in the immediate proximity of the edges of the spans can be provided with longitudinal ridges 15, which increase the surface area of the wall and thus increase the radiation therefrom. The plurality of parallel longitudinal ridges 15, extending from the outer surface of the wall of the heating channel 12 toward the edge of the belt span, have a further function. They form with the adjacent edge surface of the belt span a labyrinth seal, retarding escape of the air streaming through the opening 13, so that a degree of excess pressure is maintained in the vicinity of the edge of the bed of roller chains 4, thus tending to prevent dirt from entering the roller chain bed.

FIG. 2 shows another embodiment of the invention in which an infrared heating element 16 is provided instead of the heating channel 12. This heating element, rod-shaped and of extended length, gives off heat by radiation. An intensive effect is achieved when, as shown, the infrared heating element 16 is positioned between the edges of the belt spans 2 and 3. In many instances, however, the thickness of the work varies and thus the distance between the belt spans 2 and 3 of the press must be adjustable, so that the heating element 16 may no longer fit therebetween. In such cases i the heating element can be located with respect to the edges of the spans 2 and 3 as shown in the position 16 in FIG. 2.

FIG. 3 illustrates schematically a further embodiment in which an inductive heating arrangement 17 which heats the edges of the belt spans 2 and 3 directly is suggested. The inductive heating arrangement induces currents in the edges of the steel spans which result in the desired increase in temperature.

In all the above embodiments the heating elements extend longitudinally along the edges of the belt spans substantially along the entire length of the pressure zone throughout which the edge temperature is to be regulated. It is also possible, however, to provide heating arrangements in accordance with the invention, which are positioned at one or more points along the edges of the spans in the pressure zone.

What is claimed is:

1. An improved continuous press including endless loops formed by conveyor belts which form opposed substantially linear spans defining a pressing zone, press platens applying pressure and heat through said travelling spans to work carried therebetween and anti friction means interposed between said platens and said spans, said anti-friction means transmitting pressure and heat between said platens and said spans, the spans having edge portions extending laterally beyond the lateral edges of said platens and said anti-friction means; the improvement comprising means for independently regulating the temperature of said edge portions of said spans.

2. The apparatus of claim 1, in which the anti-friction means interposed between said platens and said spans comprise a multiplicity of endless loops of roller chains forming a bed of rollers interposed between said platens and said spans. I

3. The apparatus of claim 2, in which said temperature regulating means comprise heating means associated with each of the edge portions of said spans.

4. The apparatus of claim 2, in which the temperature regulating means comprise a heating channel for receiving a fluid heat carrier medium associated with 6. The apparatus of claim 2, in which the temperature regulating means comprise rod-shaped infrared heat elements positioned longitudinally between each pair of opposite edge portions of said spans.

7. The apparatus of claim 2, in which the temperature regulating means comprise electrical heating apparatus operating directly upon each of said edge portions of the spans.

8. The apparatus of claim 7, in which the electrical heating apparatus comprises an inductive heating arrangement. 

1. An improved continuous press including endless loops formed by conveyor belts which form opposed substantially linear spans defining a pressing zone, press platens applying pressure and heat through said travelling spans to work carried therebetween and anti-friction means interposed between said platens and said spans, said anti-friction means transmitting pressure and heat between said platens and said spans, the spans having edge portions extending laterally beyond the lateral edges of said platens and said anti-friction means; the improvement comprising means for independently regulating the temperature of said edge portions of said spans.
 2. The apparatus of claim 1, in which the anti-friction means interposed between said platens and said spans comprise a multiplicity of endless loops of roller chains forming a bed of rollers interposed between said platens and said spans.
 3. The apparatus of claim 2, in which said temperature regulating means comprise heating means associated with each of the edge portions of said spans.
 4. The apparatus of claim 2, in which the temperature regulating means comprise a heating channel for receiving a fluid heat carrier medium associated with each of the edge portions of the spans, each such channel extending longitudinally adjacent said associated edge portion.
 5. The apparatus of claim 4, in which each heating channel comprises an air duct adjacent to a lateral edge of said bed of rollers, said air duct having an opening extending longitudinally therein adjacent to said lateral edge of said bed of rollers, the outer wall of said air duct immediately adjacent said associated edge portion having longitudinal ridges extending therefrom toward said associated edge portion and forming a labyrinth seal with said edge portion.
 6. The apparatus of claim 2, in which the temperature regulating means comprise rod-shaped infrared heat elements positioned longitudinally between each pair of opposite edge portions of said spans.
 7. The apparatus of claim 2, in which the temperature regulating means comprise electrical heating apparatus operating directly upon each of said Edge portions of the spans.
 8. The apparatus of claim 7, in which the electrical heating apparatus comprises an inductive heating arrangement. 